From the prior art, different methods are known for recognizing forged bank notes. Composed forgeries whose individual parts are glued together with adhesive tape can in some cases be found indirectly via recognition of the adhesive tape by means of a reflectance measurement. However, this is not possible in every case of a glued-together composed forgery. For an authenticity check the bank notes are furthermore checked for example for properties distinguishing authentic bank-note paper from ordinary paper, for example for its fluorescence properties. Many composed forgeries consist partly of authentic paper and partly of forged paper possessing similar fluorescence properties to authentic bank notes, however. Moreover, forgeries are also assembled that consist exclusively of parts of authentic bank notes. With conventional methods it is not possible to reliably recognize those composed forgeries that provide comparable measuring signals, e.g. fluorescence signals, to authentic bank notes.